09 February 2012


Bear Glacier, Alaska. Via.
A new paper in Nature calculates that total global ice mass lost from Greenland, Antarctica, and all Earth's glaciers and ice caps between 2003 and 2010 was about 4.3 trillion tons (1,000 cubic miles).
That's enough melted ice to drive up global sea level by 0.5 inches (12 millimeters).
And that's enough water to cover the US to 1.5 feet deep (0.5 meters deep).

Glacier melt tunnel. Credit: Dook Cook | DougAK via Flickr.
The research was based on satellite measurements of ice loss from all Earth's land ice collected over eight years—with attention paid to rarely-observed glaciers and ice caps outside of Greenland and Antarctica.
The findings:

  • About a quarter of the average annual ice loss came from glaciers and ice caps outside of Greenland and Antarctica (roughly 148 billion tons, or 39 cubic miles). 
  • Ice loss from Greenland and Antarctica and their peripheral ice caps and glaciers averaged 385 billion tons (100 cubic miles) a year.

Glacier Bay, Alaska. Credit: NPS.
Traditional estimates of Earth's ice caps and glaciers have been made using ground measurements from only a few hundred of the roughly 200,000 glaciers worldwide.
This video explains some of those traditional ground-based measurement techniques.

This video describes how the GRACE satellite measurements work.

One positive finding of the satellite study was that ice loss from high the high Asian ranges—from the Himalaya, Pamir, and Tien Shan mountains—was only about 4 billion tons of ice a year. Previous ground-based estimates ranged as high as 50 billion tons a year.
From NASA News:

"This study finds that the world's small glaciers and ice caps in places like Alaska, South America and the Himalayas contribute about 0.02 inches per year to sea level rise," said Tom Wagner, cryosphere program scientist at NASA Headquarters in Washington. "While this is lower than previous estimates, it confirms that ice is being lost from around the globe, with just a few areas in precarious balance. The results sharpen our view of land-ice melting, which poses the biggest, most threatening factor in future sea level rise." 

Bering Glacier, Alaska. Credit: NASA.

The paper:
  • Thomas Jacob, John Wahr, W. Tad Pfeffer & Sean Swenson. Recent contributions of glaciers and ice caps to sea level rise. Nature. DOI:10.1038/nature10847
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